For the majority of their operation, landing gears support an aircraft while it is stationary on the ground. However, landing gears must also be able to support the aircraft when it is landing and moving on the ground. Thus, landing gears must be able to support not only the weight of the aircraft, but also the additional forces created when the aircraft lands and moves on the ground.
Also, when deployed, landing gears must place their associated wheel(s) in the appropriate position relative to the rest of the aircraft because the placement of the wheels affects the ground operations of the aircraft. For example, placing the wheels of the main landing gears too close to the longitudinal centerline of the aircraft will allow the aircraft to easily tip over. Furthermore, because the center of gravity of the aircraft is usually forward of the wheels of the main landing gears, placing these wheels too far aft on the aircraft will cause the aircraft to require additional force to rotate upwards during takeoff, requiring larger takeoff distances or horizontal control surfaces. Thus, upon deployment, landing gears must place their associated wheel(s) in the appropriate position as well as support the aircraft during its different modes of operation on the ground.
In addition, most landing gears must be retractable in order that they may be stowed within the skin of the aircraft after takeoff, which reduces aerodynamic drag. Because they are stowed within the skin of the airframe, reducing the space that landing gears require for stowage assists in reducing aerodynamic drag by reducing the lateral cross-section of the aircraft and/or allows more payload to be carried within the same lateral cross-section. Thus, landing gears that stow compactly are preferable.
Unfortunately, landing gears that stow compactly usually have many more components relative to non-compact landing gears, leading to increased manufacturing, installation, and maintenance costs. Moreover, as the number of components increases, the strength of the landing gears becomes a concern, especially if the landing gears must upon deployment place their associated wheel(s) far from the point where the landing gears couple to the aircraft.
The present invention provides landing gears that substantially reduce or eliminate at least some of the disadvantages and problems associated with previously developed landing gears. Accordingly, in certain embodiments, the present invention provides a landing gear that can place a wheel relatively far from the point where the landing gear couples to an airframe and yet be stowed in a relatively compact space within the airframe.
In particular embodiments, the landing gear includes a trunnion, a subframe, and a wheel. The trunnion has at least one principal pivot point, which is adapted to be pivotably coupled to an airframe to allow the trunnion to pivot about a principal trunnion pivot axis. The trunnion is operable to move between a deployed position and a stowed position by pivoting about the principal trunnion pivot axis. The trunnion further includes at least one secondary pivot point. The subframe also has at least one principal pivot point. This principal pivot point is pivotably coupled to the secondary pivot point of the trunnion to allow the subframe to pivot about a principal subframe pivot axis. The subframe is operable to move between a deployed position and a stowed position by pivoting about the principal subframe pivot axis. The wheel is rotatably coupled to the subframe and is moved to a stowed position when the subframe pivots from the deployed position to the stowed position about the principal subframe pivot axis and the trunnion pivots from the deployed position to the stowed position about the principal trunnion pivot axis.
In other embodiments, the present invention provides an aircraft utilizing a landing gear. The aircraft includes an airframe and a landing gear coupled to the airframe. The landing gear includes a trunnion having at least one principal pivot point, which is pivotably coupled to the airframe to allow the trunnion to pivot about a principal trunnion pivot axis. The trunnion is operable to move between a deployed position and a stowed position by pivoting about the principal trunnion pivot axis. The trunnion further includes at least one secondary pivot point. The landing gear also includes a subframe having at least one principal pivot point, which is pivotably coupled to the secondary pivot point of the trunnion to allow the subframe to pivot about a principal subframe pivot axis. The subframe is operable to move between a deployed position and a stowed position by pivoting about the principal subframe pivot axis. The landing gear further includes a wheel rotatably coupled to the subframe. The wheel is moved to a stowed position when the subframe pivots from the deployed position to the stowed position about the principal subframe pivot axis and the trunnion pivots from the deployed position to the stowed position about the principal trunnion pivot axis.
The present invention has several technical features and advantages. For example, in particular embodiments, the landing gear can place an associated wheel in the appropriate position relative to the airframe even if the position is relatively far from the point where the landing gear couples to the airframe. Thus, the landing gear can still place the associated wheel in the appropriate position relative to the airframe even when the landing gear must couple to the airframe relatively far from the position where the wheel is to be placed upon deployment. As another example, in certain embodiments, the landing gear can stow compactly within the skin of the airframe, which improves aerodynamic performance and/or cargo capacity of the aircraft. As a further example, in some embodiments, the landing gear may have a relatively small number of components, allowing for easy manufacture, installation, and maintenance of the landing gear. As an additional example, in several embodiments, the landing gear uses a box design for the trunnion, which reduces the weight of the landing gear. Of course, some embodiments possess multiple advantages and technical features.
Other technical features and advantages will be readily apparent to one of skill in the art from the following figures, description, and claims.